Three loud explosions shook central Baghdad in quick succession today, killing at least 12 people and breaking a period of relative calm in the Iraqi capital after elections last month.

One of the blasts struck near the Iranian Embassy, said Major General Qassim al-Moussawi, a spokesman for the city's operations command centre. The other two were in western Baghdad.

At least 12 people were killed and 42 were injured in the explosion outside the embassy, which was believed to have been caused by an explosives-packed car driven by a suicide attacker, according to two police officers and a hospital doctor. They said many of the victims were employees at a nearby state-run bank.

Iran's ambassador to Iraq, Hasan Kazemi Qomi, said it was unclear whether the blast was targeting the embassy itself.

"The explosion happened at the embassy gate, targeting visitors and Iraqi police," he said. "There was some damage to the embassy building but no employees were harmed inside."

The force of the blasts shook buildings and rattled windows in the centre of the capital. At least two plumes of grey smoke rose above the capital, one near the centre of the city and another in the western part of the capital.

The blasts come two days after an execution-style attack in which at least 24 Sunnis were killed. The slayings reignited fears of the sectarian fighting in 2006 and 2007.

The bloodshed comes amid increasing concerns that insurgents will take advantage of Iraq's political turmoil to further destabilise the country, nearly a month after parliamentary elections failed to give any candidate a decisive win.

Many fear a drawn-out political debate could spill over into violence and complicate American efforts to speed up troop withdrawals in the coming months.

Footage aired on state television shortly after the blasts showed bystanders near the Iranian Embassy loading casualties into police vehicles and ambulances. One man was carrying the body of a small girl.

The explosions, which occurred shortly before 10.30am, came after a number of far smaller blasts overnight. One of those earlier blasts, believed to be caused by a bomb underneath a parked car, killed one civilian and injured nine others, according to police.